Indeed, in The Lord of the Sands of Time, travelers from the twenty-sixth century travel back to the second century AD in order to propagate a set of Laws that declare catastrophe to be inevitable and cooperation between peoples the only hope for survival.

As far as the argument that governments should not subsidize infrastructure in support of that transport task because the weighted average of the income of those travelers is higher than the national median income … its bizarre to introduce that for HSR but not for public subsidies for air travel infrastructure or public subsidies for road travel infrastructure.